2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 TcMatches: Typecheck some @Matches@
9 module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
11 tcStmts, tcStmtsAndThen, tcDoStmts, tcBody,
12 tcDoStmt, tcMDoStmt, tcGuardStmt
15 import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRhoNC, tcCheckId,
16 tcMonoExpr, tcMonoExprNC, tcPolyExpr )
32 import Coercion ( mkSymCoI )
38 -- Create chunkified tuple tybes for monad comprehensions
43 #include "HsVersions.h"
46 %************************************************************************
48 \subsection{tcMatchesFun, tcMatchesCase}
50 %************************************************************************
52 @tcMatchesFun@ typechecks a @[Match]@ list which occurs in a
53 @FunMonoBind@. The second argument is the name of the function, which
54 is used in error messages. It checks that all the equations have the
55 same number of arguments before using @tcMatches@ to do the work.
57 Note [Polymorphic expected type for tcMatchesFun]
58 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
59 tcMatchesFun may be given a *sigma* (polymorphic) type
60 so it must be prepared to use tcGen to skolemise it.
61 See Note [sig_tau may be polymorphic] in TcPat.
64 tcMatchesFun :: Name -> Bool
66 -> TcSigmaType -- Expected type of function
67 -> TcM (HsWrapper, MatchGroup TcId) -- Returns type of body
68 tcMatchesFun fun_name inf matches exp_ty
69 = do { -- Check that they all have the same no of arguments
70 -- Location is in the monad, set the caller so that
71 -- any inter-equation error messages get some vaguely
72 -- sensible location. Note: we have to do this odd
73 -- ann-grabbing, because we don't always have annotations in
74 -- hand when we call tcMatchesFun...
75 traceTc "tcMatchesFun" (ppr fun_name $$ ppr exp_ty)
76 ; checkArgs fun_name matches
78 ; (wrap_gen, (wrap_fun, group))
79 <- tcGen (FunSigCtxt fun_name) exp_ty $ \ _ exp_rho ->
80 -- Note [Polymorphic expected type for tcMatchesFun]
81 matchFunTys herald arity exp_rho $ \ pat_tys rhs_ty ->
82 tcMatches match_ctxt pat_tys rhs_ty matches
83 ; return (wrap_gen <.> wrap_fun, group) }
85 arity = matchGroupArity matches
86 herald = ptext (sLit "The equation(s) for")
87 <+> quotes (ppr fun_name) <+> ptext (sLit "have")
88 match_ctxt = MC { mc_what = FunRhs fun_name inf, mc_body = tcBody }
91 @tcMatchesCase@ doesn't do the argument-count check because the
92 parser guarantees that each equation has exactly one argument.
95 tcMatchesCase :: TcMatchCtxt -- Case context
96 -> TcRhoType -- Type of scrutinee
97 -> MatchGroup Name -- The case alternatives
98 -> TcRhoType -- Type of whole case expressions
99 -> TcM (MatchGroup TcId) -- Translated alternatives
101 tcMatchesCase ctxt scrut_ty matches res_ty
102 | isEmptyMatchGroup matches -- Allow empty case expressions
103 = return (MatchGroup [] (mkFunTys [scrut_ty] res_ty))
106 = tcMatches ctxt [scrut_ty] res_ty matches
108 tcMatchLambda :: MatchGroup Name -> TcRhoType -> TcM (HsWrapper, MatchGroup TcId)
109 tcMatchLambda match res_ty
110 = matchFunTys herald n_pats res_ty $ \ pat_tys rhs_ty ->
111 tcMatches match_ctxt pat_tys rhs_ty match
113 n_pats = matchGroupArity match
114 herald = sep [ ptext (sLit "The lambda expression")
115 <+> quotes (pprSetDepth (PartWay 1) $
116 pprMatches (LambdaExpr :: HsMatchContext Name) match),
117 -- The pprSetDepth makes the abstraction print briefly
119 match_ctxt = MC { mc_what = LambdaExpr,
123 @tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@.
126 tcGRHSsPat :: GRHSs Name -> TcRhoType -> TcM (GRHSs TcId)
127 -- Used for pattern bindings
128 tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty
130 match_ctxt = MC { mc_what = PatBindRhs,
137 :: SDoc -- See Note [Herald for matchExpecteFunTys] in TcUnify
140 -> ([TcSigmaType] -> TcRhoType -> TcM a)
141 -> TcM (HsWrapper, a)
143 -- Written in CPS style for historical reasons;
144 -- could probably be un-CPSd, like matchExpectedTyConApp
146 matchFunTys herald arity res_ty thing_inside
147 = do { (coi, pat_tys, res_ty) <- matchExpectedFunTys herald arity res_ty
148 ; res <- thing_inside pat_tys res_ty
149 ; return (coiToHsWrapper (mkSymCoI coi), res) }
152 %************************************************************************
156 %************************************************************************
159 tcMatches :: TcMatchCtxt
160 -> [TcSigmaType] -- Expected pattern types
161 -> TcRhoType -- Expected result-type of the Match.
163 -> TcM (MatchGroup TcId)
165 data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module
166 = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is
167 mc_body :: LHsExpr Name -- Type checker for a body of
170 -> TcM (LHsExpr TcId) }
172 tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _)
173 = ASSERT( not (null matches) ) -- Ensure that rhs_ty is filled in
174 do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
175 ; return (MatchGroup matches' (mkFunTys pat_tys rhs_ty)) }
178 tcMatch :: TcMatchCtxt
179 -> [TcSigmaType] -- Expected pattern types
180 -> TcRhoType -- Expected result-type of the Match.
184 tcMatch ctxt pat_tys rhs_ty match
185 = wrapLocM (tc_match ctxt pat_tys rhs_ty) match
187 tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss)
188 = add_match_ctxt match $
189 do { (pats', grhss') <- tcPats (mc_what ctxt) pats pat_tys $
190 tc_grhss ctxt maybe_rhs_sig grhss rhs_ty
191 ; return (Match pats' Nothing grhss') }
193 tc_grhss ctxt Nothing grhss rhs_ty
194 = tcGRHSs ctxt grhss rhs_ty -- No result signature
196 -- Result type sigs are no longer supported
197 tc_grhss _ (Just {}) _ _
198 = panic "tc_ghrss" -- Rejected by renamer
200 -- For (\x -> e), tcExpr has already said "In the expresssion \x->e"
201 -- so we don't want to add "In the lambda abstraction \x->e"
202 add_match_ctxt match thing_inside
203 = case mc_what ctxt of
204 LambdaExpr -> thing_inside
205 m_ctxt -> addErrCtxt (pprMatchInCtxt m_ctxt match) thing_inside
208 tcGRHSs :: TcMatchCtxt -> GRHSs Name -> TcRhoType
211 -- Notice that we pass in the full res_ty, so that we get
212 -- good inference from simple things like
213 -- f = \(x::forall a.a->a) -> <stuff>
214 -- We used to force it to be a monotype when there was more than one guard
215 -- but we don't need to do that any more
217 tcGRHSs ctxt (GRHSs grhss binds) res_ty
218 = do { (binds', grhss') <- tcLocalBinds binds $
219 mapM (wrapLocM (tcGRHS ctxt res_ty)) grhss
221 ; return (GRHSs grhss' binds') }
224 tcGRHS :: TcMatchCtxt -> TcRhoType -> GRHS Name -> TcM (GRHS TcId)
226 tcGRHS ctxt res_ty (GRHS guards rhs)
227 = do { (guards', rhs') <- tcStmtsAndThen stmt_ctxt tcGuardStmt guards res_ty $
229 ; return (GRHS guards' rhs') }
231 stmt_ctxt = PatGuard (mc_what ctxt)
235 %************************************************************************
237 \subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
239 %************************************************************************
242 tcDoStmts :: HsStmtContext Name
245 -> TcM (HsExpr TcId) -- Returns a HsDo
246 tcDoStmts ListComp stmts res_ty
247 = do { (coi, elt_ty) <- matchExpectedListTy res_ty
248 ; stmts' <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty
249 ; return $ mkHsWrapCoI coi
250 (HsDo ListComp stmts' (mkListTy elt_ty)) }
252 tcDoStmts PArrComp stmts res_ty
253 = do { (coi, elt_ty) <- matchExpectedPArrTy res_ty
254 ; stmts' <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty
255 ; return $ mkHsWrapCoI coi
256 (HsDo PArrComp stmts' (mkPArrTy elt_ty)) }
258 tcDoStmts DoExpr stmts res_ty
259 = do { stmts' <- tcStmts DoExpr tcDoStmt stmts res_ty
260 ; return (HsDo DoExpr stmts' res_ty) }
262 tcDoStmts MDoExpr stmts res_ty
263 = do { stmts' <- tcStmts MDoExpr tcDoStmt stmts res_ty
264 ; return (HsDo MDoExpr stmts' res_ty) }
266 tcDoStmts MonadComp stmts res_ty
267 = do { stmts' <- tcStmts MonadComp tcMcStmt stmts res_ty
268 ; return (HsDo MonadComp stmts' res_ty) }
270 tcDoStmts ctxt _ _ = pprPanic "tcDoStmts" (pprStmtContext ctxt)
272 tcBody :: LHsExpr Name -> TcRhoType -> TcM (LHsExpr TcId)
274 = do { traceTc "tcBody" (ppr res_ty)
275 ; body' <- tcMonoExpr body res_ty
281 %************************************************************************
285 %************************************************************************
289 = forall thing. HsStmtContext Name
291 -> TcRhoType -- Result type for comprehension
292 -> (TcRhoType -> TcM thing) -- Checker for what follows the stmt
293 -> TcM (Stmt TcId, thing)
295 tcStmts :: HsStmtContext Name
296 -> TcStmtChecker -- NB: higher-rank type
300 tcStmts ctxt stmt_chk stmts res_ty
301 = do { (stmts', _) <- tcStmtsAndThen ctxt stmt_chk stmts res_ty $
305 tcStmtsAndThen :: HsStmtContext Name
306 -> TcStmtChecker -- NB: higher-rank type
309 -> (TcRhoType -> TcM thing)
310 -> TcM ([LStmt TcId], thing)
312 -- Note the higher-rank type. stmt_chk is applied at different
313 -- types in the equations for tcStmts
315 tcStmtsAndThen _ _ [] res_ty thing_inside
316 = do { thing <- thing_inside res_ty
317 ; return ([], thing) }
319 -- LetStmts are handled uniformly, regardless of context
320 tcStmtsAndThen ctxt stmt_chk (L loc (LetStmt binds) : stmts) res_ty thing_inside
321 = do { (binds', (stmts',thing)) <- tcLocalBinds binds $
322 tcStmtsAndThen ctxt stmt_chk stmts res_ty thing_inside
323 ; return (L loc (LetStmt binds') : stmts', thing) }
325 -- For the vanilla case, handle the location-setting part
326 tcStmtsAndThen ctxt stmt_chk (L loc stmt : stmts) res_ty thing_inside
327 = do { (stmt', (stmts', thing)) <-
329 addErrCtxt (pprStmtInCtxt ctxt stmt) $
330 stmt_chk ctxt stmt res_ty $ \ res_ty' ->
332 tcStmtsAndThen ctxt stmt_chk stmts res_ty' $
334 ; return (L loc stmt' : stmts', thing) }
336 --------------------------------
338 tcGuardStmt :: TcStmtChecker
339 tcGuardStmt _ (ExprStmt guard _ _ _) res_ty thing_inside
340 = do { guard' <- tcMonoExpr guard boolTy
341 ; thing <- thing_inside res_ty
342 ; return (ExprStmt guard' noSyntaxExpr noSyntaxExpr boolTy, thing) }
344 tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside
345 = do { (rhs', rhs_ty) <- tcInferRhoNC rhs -- Stmt has a context already
346 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat rhs_ty $
348 ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
350 tcGuardStmt _ stmt _ _
351 = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt)
354 --------------------------------
355 -- List comprehensions and PArrays
357 tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray)
360 tcLcStmt _ _ (LastStmt body _) elt_ty thing_inside
361 = do { body' <- tcMonoExpr body elt_ty
362 ; thing <- thing_inside (panic "tcLcStmt: thing_inside")
363 ; return (LastStmt body' noSyntaxExpr, thing) }
365 -- A generator, pat <- rhs
366 tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) elt_ty thing_inside
367 = do { pat_ty <- newFlexiTyVarTy liftedTypeKind
368 ; rhs' <- tcMonoExpr rhs (mkTyConApp m_tc [pat_ty])
369 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
371 ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
374 tcLcStmt _ _ (ExprStmt rhs _ _ _) elt_ty thing_inside
375 = do { rhs' <- tcMonoExpr rhs boolTy
376 ; thing <- thing_inside elt_ty
377 ; return (ExprStmt rhs' noSyntaxExpr noSyntaxExpr boolTy, thing) }
379 -- A parallel set of comprehensions
380 -- [ (g x, h x) | ... ; let g v = ...
381 -- | ... ; let h v = ... ]
383 -- It's possible that g,h are overloaded, so we need to feed the LIE from the
384 -- (g x, h x) up through both lots of bindings (so we get the bindLocalMethods).
385 -- Similarly if we had an existential pattern match:
387 -- data T = forall a. Show a => C a
389 -- [ (show x, show y) | ... ; C x <- ...
390 -- | ... ; C y <- ... ]
392 -- Then we need the LIE from (show x, show y) to be simplified against
393 -- the bindings for x and y.
395 -- It's difficult to do this in parallel, so we rely on the renamer to
396 -- ensure that g,h and x,y don't duplicate, and simply grow the environment.
397 -- So the binders of the first parallel group will be in scope in the second
398 -- group. But that's fine; there's no shadowing to worry about.
400 tcLcStmt m_tc ctxt (ParStmt bndr_stmts_s _ _ _) elt_ty thing_inside
401 = do { (pairs', thing) <- loop bndr_stmts_s
402 ; return (ParStmt pairs' noSyntaxExpr noSyntaxExpr noSyntaxExpr, thing) }
404 -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing)
405 loop [] = do { thing <- thing_inside elt_ty
406 ; return ([], thing) } -- matching in the branches
408 loop ((stmts, names) : pairs)
409 = do { (stmts', (ids, pairs', thing))
410 <- tcStmtsAndThen ctxt (tcLcStmt m_tc) stmts elt_ty $ \ _elt_ty' ->
411 do { ids <- tcLookupLocalIds names
412 ; (pairs', thing) <- loop pairs
413 ; return (ids, pairs', thing) }
414 ; return ( (stmts', ids) : pairs', thing ) }
416 tcLcStmt m_tc ctxt (TransformStmt stmts binders usingExpr maybeByExpr _ _) elt_ty thing_inside = do
417 (stmts', (binders', usingExpr', maybeByExpr', thing)) <-
418 tcStmtsAndThen (TransformStmtCtxt ctxt) (tcLcStmt m_tc) stmts elt_ty $ \elt_ty' -> do
419 let alphaListTy = mkTyConApp m_tc [alphaTy]
421 (usingExpr', maybeByExpr') <-
424 -- We must validate that usingExpr :: forall a. [a] -> [a]
425 let using_ty = mkForAllTy alphaTyVar (alphaListTy `mkFunTy` alphaListTy)
426 usingExpr' <- tcPolyExpr usingExpr using_ty
427 return (usingExpr', Nothing)
429 -- We must infer a type such that e :: t and then check that
430 -- usingExpr :: forall a. (a -> t) -> [a] -> [a]
431 (byExpr', tTy) <- tcInferRhoNC byExpr
432 let using_ty = mkForAllTy alphaTyVar $
433 (alphaTy `mkFunTy` tTy)
434 `mkFunTy` alphaListTy `mkFunTy` alphaListTy
435 usingExpr' <- tcPolyExpr usingExpr using_ty
436 return (usingExpr', Just byExpr')
438 binders' <- tcLookupLocalIds binders
439 thing <- thing_inside elt_ty'
441 return (binders', usingExpr', maybeByExpr', thing)
443 return (TransformStmt stmts' binders' usingExpr' maybeByExpr' noSyntaxExpr noSyntaxExpr, thing)
445 tcLcStmt m_tc ctxt (GroupStmt { grpS_stmts = stmts, grpS_bndrs = bindersMap
446 , grpS_by = by, grpS_using = using
447 , grpS_explicit = explicit }) elt_ty thing_inside
448 = do { let (bndr_names, list_bndr_names) = unzip bindersMap
450 ; (stmts', (bndr_ids, by', using_ty, elt_ty')) <-
451 tcStmtsAndThen (TransformStmtCtxt ctxt) (tcLcStmt m_tc) stmts elt_ty $ \elt_ty' -> do
454 Nothing -> -- check that using :: forall a. [a] -> [[a]]
455 return (Nothing, mkForAllTy alphaTyVar $
456 alphaListTy `mkFunTy` alphaListListTy)
458 Just by_e -> -- check that using :: forall a. (a -> t) -> [a] -> [[a]]
460 do { (by_e', t_ty) <- tcInferRhoNC by_e
461 ; return (Just by_e', mkForAllTy alphaTyVar $
462 (alphaTy `mkFunTy` t_ty)
463 `mkFunTy` alphaListTy
464 `mkFunTy` alphaListListTy) }
465 -- Find the Ids (and hence types) of all old binders
466 bndr_ids <- tcLookupLocalIds bndr_names
468 return (bndr_ids, by', using_ty, elt_ty')
470 -- Ensure that every old binder of type b is linked up with
471 -- its new binder which should have type [b]
472 ; let list_bndr_ids = zipWith mk_list_bndr list_bndr_names bndr_ids
473 bindersMap' = bndr_ids `zip` list_bndr_ids
474 -- See Note [GroupStmt binder map] in HsExpr
476 ; using' <- tcPolyExpr using using_ty
478 -- Type check the thing in the environment with
479 -- these new binders and return the result
480 ; thing <- tcExtendIdEnv list_bndr_ids (thing_inside elt_ty')
481 ; return (emptyGroupStmt { grpS_stmts = stmts', grpS_bndrs = bindersMap'
482 , grpS_by = by', grpS_using = using'
483 , grpS_explicit = explicit }, thing) }
485 alphaListTy = mkTyConApp m_tc [alphaTy]
486 alphaListListTy = mkTyConApp m_tc [alphaListTy]
488 mk_list_bndr :: Name -> TcId -> TcId
489 mk_list_bndr list_bndr_name bndr_id
490 = mkLocalId list_bndr_name (mkTyConApp m_tc [idType bndr_id])
492 tcLcStmt _ _ stmt _ _
493 = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt)
496 --------------------------------
497 -- Monad comprehensions
499 tcMcStmt :: TcStmtChecker
501 tcMcStmt _ (LastStmt body return_op) res_ty thing_inside
502 = do { a_ty <- newFlexiTyVarTy liftedTypeKind
503 ; return_op' <- tcSyntaxOp MCompOrigin return_op
504 (a_ty `mkFunTy` res_ty)
505 ; body' <- tcMonoExpr body a_ty
506 ; thing <- thing_inside (panic "tcMcStmt: thing_inside")
507 ; return (LastStmt body' return_op', thing) }
509 -- Generators for monad comprehensions ( pat <- rhs )
511 -- [ body | q <- gen ] -> gen :: m a
515 tcMcStmt ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
516 = do { rhs_ty <- newFlexiTyVarTy liftedTypeKind
517 ; pat_ty <- newFlexiTyVarTy liftedTypeKind
518 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
520 -- (>>=) :: rhs_ty -> (pat_ty -> new_res_ty) -> res_ty
521 ; bind_op' <- tcSyntaxOp MCompOrigin bind_op
522 (mkFunTys [rhs_ty, mkFunTy pat_ty new_res_ty] res_ty)
524 -- If (but only if) the pattern can fail, typecheck the 'fail' operator
525 ; fail_op' <- if isIrrefutableHsPat pat
526 then return noSyntaxExpr
527 else tcSyntaxOp MCompOrigin fail_op (mkFunTy stringTy new_res_ty)
529 ; rhs' <- tcMonoExprNC rhs rhs_ty
530 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
531 thing_inside new_res_ty
533 ; return (BindStmt pat' rhs' bind_op' fail_op', thing) }
535 -- Boolean expressions.
537 -- [ body | stmts, expr ] -> expr :: m Bool
539 tcMcStmt _ (ExprStmt rhs then_op guard_op _) res_ty thing_inside
540 = do { -- Deal with rebindable syntax:
541 -- guard_op :: test_ty -> rhs_ty
542 -- then_op :: rhs_ty -> new_res_ty -> res_ty
543 -- Where test_ty is, for example, Bool
544 test_ty <- newFlexiTyVarTy liftedTypeKind
545 ; rhs_ty <- newFlexiTyVarTy liftedTypeKind
546 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
547 ; rhs' <- tcMonoExpr rhs test_ty
548 ; guard_op' <- tcSyntaxOp MCompOrigin guard_op
549 (mkFunTy test_ty rhs_ty)
550 ; then_op' <- tcSyntaxOp MCompOrigin then_op
551 (mkFunTys [rhs_ty, new_res_ty] res_ty)
552 ; thing <- thing_inside new_res_ty
553 ; return (ExprStmt rhs' then_op' guard_op' rhs_ty, thing) }
555 -- Transform statements.
557 -- [ body | stmts, then f ] -> f :: forall a. m a -> m a
558 -- [ body | stmts, then f by e ] -> f :: forall a. (a -> t) -> m a -> m a
560 tcMcStmt ctxt (TransformStmt stmts binders usingExpr maybeByExpr return_op bind_op) res_ty thing_inside
562 -- We don't know the types of binders yet, so we use this dummy and
563 -- later unify this type with the `m_bndr_ty`
564 ty_dummy <- newFlexiTyVarTy liftedTypeKind
566 ; (stmts', (binders', usingExpr', maybeByExpr', return_op', bind_op', thing)) <-
567 tcStmtsAndThen (TransformStmtCtxt ctxt) tcMcStmt stmts ty_dummy $ \res_ty' -> do
568 { (_, (m_ty, _)) <- matchExpectedAppTy res_ty'
569 ; (usingExpr', maybeByExpr') <-
572 -- We must validate that usingExpr :: forall a. m a -> m a
573 let using_ty = mkForAllTy alphaTyVar $
574 (m_ty `mkAppTy` alphaTy)
576 (m_ty `mkAppTy` alphaTy)
577 usingExpr' <- tcPolyExpr usingExpr using_ty
578 return (usingExpr', Nothing)
580 -- We must infer a type such that e :: t and then check that
581 -- usingExpr :: forall a. (a -> t) -> m a -> m a
582 (byExpr', tTy) <- tcInferRhoNC byExpr
583 let using_ty = mkForAllTy alphaTyVar $
584 (alphaTy `mkFunTy` tTy)
586 (m_ty `mkAppTy` alphaTy)
588 (m_ty `mkAppTy` alphaTy)
589 usingExpr' <- tcPolyExpr usingExpr using_ty
590 return (usingExpr', Just byExpr')
592 ; bndr_ids <- tcLookupLocalIds binders
594 -- `return` and `>>=` are used to pass around/modify our
595 -- binders, so we know their types:
597 -- return :: (a,b,c,..) -> m (a,b,c,..)
598 -- (>>=) :: m (a,b,c,..)
599 -- -> ( (a,b,c,..) -> m (a,b,c,..) )
602 ; let bndr_ty = mkBigCoreVarTupTy bndr_ids
603 m_bndr_ty = m_ty `mkAppTy` bndr_ty
605 ; return_op' <- tcSyntaxOp MCompOrigin return_op
606 (bndr_ty `mkFunTy` m_bndr_ty)
608 ; bind_op' <- tcSyntaxOp MCompOrigin bind_op $
609 m_bndr_ty `mkFunTy` (bndr_ty `mkFunTy` res_ty)
612 -- Unify types of the inner comprehension and the binders type
613 ; _ <- unifyType res_ty' m_bndr_ty
615 -- Typecheck the `thing` with out old type (which is the type
616 -- of the final result of our comprehension)
617 ; thing <- thing_inside res_ty
619 ; return (bndr_ids, usingExpr', maybeByExpr', return_op', bind_op', thing) }
621 ; return (TransformStmt stmts' binders' usingExpr' maybeByExpr' return_op' bind_op', thing) }
623 -- Grouping statements
625 -- [ body | stmts, then group by e ]
627 -- [ body | stmts, then group by e using f ]
629 -- f :: forall a. (a -> t) -> m a -> m (m a)
630 -- [ body | stmts, then group using f ]
631 -- -> f :: forall a. m a -> m (m a)
633 tcMcStmt ctxt (GroupStmt { grpS_stmts = stmts, grpS_bndrs = bindersMap
634 , grpS_by = by, grpS_using = using, grpS_explicit = explicit
635 , grpS_ret = return_op, grpS_bind = bind_op
636 , grpS_fmap = fmap_op }) res_ty thing_inside
637 = do { let star_star_kind = liftedTypeKind `mkArrowKind` liftedTypeKind
638 ; m1_ty <- newFlexiTyVarTy star_star_kind
639 ; m2_ty <- newFlexiTyVarTy star_star_kind
640 ; n_ty <- newFlexiTyVarTy star_star_kind
641 ; tup_ty_var <- newFlexiTyVarTy liftedTypeKind
642 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
643 ; let (bndr_names, n_bndr_names) = unzip bindersMap
644 m1_tup_ty = m1_ty `mkAppTy` tup_ty_var
646 -- 'stmts' returns a result of type (m1_ty tuple_ty),
647 -- typically something like [(Int,Bool,Int)]
648 -- We don't know what tuple_ty is yet, so we use a variable
649 ; (stmts', (bndr_ids, by_e_ty, return_op')) <-
650 tcStmtsAndThen (TransformStmtCtxt ctxt) tcMcStmt stmts m1_tup_ty $ \res_ty' -> do
651 { by_e_ty <- case by of
652 Nothing -> return Nothing
653 Just e -> do { e_ty <- tcInferRhoNC e; return (Just e_ty) }
655 -- Find the Ids (and hence types) of all old binders
656 ; bndr_ids <- tcLookupLocalIds bndr_names
658 -- 'return' is only used for the binders, so we know its type.
660 -- return :: (a,b,c,..) -> m (a,b,c,..)
661 ; return_op' <- tcSyntaxOp MCompOrigin return_op $
662 (mkBigCoreVarTupTy bndr_ids) `mkFunTy` res_ty'
664 ; return (bndr_ids, by_e_ty, return_op') }
668 ; let tup_ty = mkBigCoreVarTupTy bndr_ids -- (a,b,c)
669 using_arg_ty = m1_ty `mkAppTy` tup_ty -- m1 (a,b,c)
670 n_tup_ty = n_ty `mkAppTy` tup_ty -- n (a,b,c)
671 using_res_ty = m2_ty `mkAppTy` n_tup_ty -- m2 (n (a,b,c))
672 using_fun_ty = using_arg_ty `mkFunTy` using_arg_ty
674 -- (>>=) :: m2 (n (a,b,c)) -> ( n (a,b,c) -> new_res_ty ) -> res_ty
675 -- using :: ((a,b,c)->t) -> m1 (a,b,c) -> m2 (n (a,b,c))
677 --------------- Typecheck the 'bind' function -------------
678 ; bind_op' <- tcSyntaxOp MCompOrigin bind_op $
679 using_res_ty `mkFunTy` (n_tup_ty `mkFunTy` new_res_ty)
682 --------------- Typecheck the 'using' function -------------
683 ; let poly_fun_ty = (m1_ty `mkAppTy` alphaTy) `mkFunTy`
684 (m2_ty `mkAppTy` (n_ty `mkAppTy` alphaTy))
685 using_poly_ty = case by_e_ty of
686 Nothing -> mkForAllTy alphaTyVar poly_fun_ty
687 -- using :: forall a. m1 a -> m2 (n a)
689 Just (_,t_ty) -> mkForAllTy alphaTyVar $
690 (alphaTy `mkFunTy` t_ty) `mkFunTy` poly_fun_ty
691 -- using :: forall a. (a->t) -> m1 a -> m2 (n a)
694 ; using' <- tcPolyExpr using using_poly_ty
695 ; coi <- unifyType (applyTy using_poly_ty tup_ty)
697 Nothing -> using_fun_ty
698 Just (_,t_ty) -> (tup_ty `mkFunTy` t_ty) `mkFunTy` using_fun_ty)
699 ; let final_using = fmap (mkHsWrapCoI coi . HsWrap (WpTyApp tup_ty)) using'
701 --------------- Typecheck the 'fmap' function -------------
702 ; fmap_op' <- fmap unLoc . tcPolyExpr (noLoc fmap_op) $
703 mkForAllTy alphaTyVar $ mkForAllTy betaTyVar $
704 (alphaTy `mkFunTy` betaTy)
705 `mkFunTy` (n_ty `mkAppTy` alphaTy)
706 `mkFunTy` (n_ty `mkAppTy` betaTy)
708 ; let mk_n_bndr :: Name -> TcId -> TcId
709 mk_n_bndr n_bndr_name bndr_id
710 = mkLocalId n_bndr_name (n_ty `mkAppTy` idType bndr_id)
712 -- Ensure that every old binder of type `b` is linked up with its
713 -- new binder which should have type `n b`
714 -- See Note [GroupStmt binder map] in HsExpr
715 n_bndr_ids = zipWith mk_n_bndr n_bndr_names bndr_ids
716 bindersMap' = bndr_ids `zip` n_bndr_ids
718 -- Type check the thing in the environment with these new binders and
720 ; thing <- tcExtendIdEnv n_bndr_ids (thing_inside res_ty)
722 ; return (GroupStmt { grpS_stmts = stmts', grpS_bndrs = bindersMap'
723 , grpS_by = fmap fst by_e_ty, grpS_using = final_using
724 , grpS_ret = return_op', grpS_bind = bind_op'
725 , grpS_fmap = fmap_op', grpS_explicit = explicit }, thing) }
727 -- Typecheck `ParStmt`. See `tcLcStmt` for more informations about typechecking
730 -- Note: The `mzip` function will get typechecked via:
732 -- ParStmt [st1::t1, st2::t2, st3::t3]
735 -- -> (m st2 -> m st3 -> m (st2, st3)) -- recursive call
736 -- -> m (st1, (st2, st3))
738 tcMcStmt ctxt (ParStmt bndr_stmts_s mzip_op bind_op return_op) res_ty thing_inside
739 = do { (_,(m_ty,_)) <- matchExpectedAppTy res_ty
740 -- ToDo: what if the coercion isn't the identity?
742 ; (pairs', thing) <- loop m_ty bndr_stmts_s
744 ; let mzip_ty = mkForAllTys [alphaTyVar, betaTyVar] $
745 (m_ty `mkAppTy` alphaTy)
747 (m_ty `mkAppTy` betaTy)
749 (m_ty `mkAppTy` mkBoxedTupleTy [alphaTy, betaTy])
750 ; mzip_op' <- unLoc `fmap` tcPolyExpr (noLoc mzip_op) mzip_ty
753 ; let tys = map (mkBigCoreVarTupTy . snd) pairs'
754 tuple_ty = mk_tuple_ty tys
756 ; bind_op' <- tcSyntaxOp MCompOrigin bind_op $
757 (m_ty `mkAppTy` tuple_ty)
759 (tuple_ty `mkFunTy` res_ty)
763 ; return_op' <- fmap unLoc . tcPolyExpr (noLoc return_op) $
764 mkForAllTy alphaTyVar $
765 alphaTy `mkFunTy` (m_ty `mkAppTy` alphaTy)
767 ; return (ParStmt pairs' mzip_op' bind_op' return_op', thing) }
769 where mk_tuple_ty tys = foldr1 (\tn tm -> mkBoxedTupleTy [tn, tm]) tys
771 -- loop :: Type -- m_ty
772 -- -> [([LStmt Name], [Name])]
773 -- -> TcM ([([LStmt TcId], [TcId])], thing)
774 loop _ [] = do { thing <- thing_inside res_ty
775 ; return ([], thing) } -- matching in the branches
777 loop m_ty ((stmts, names) : pairs)
778 = do { -- type dummy since we don't know all binder types yet
779 ty_dummy <- newFlexiTyVarTy liftedTypeKind
780 ; (stmts', (ids, pairs', thing))
781 <- tcStmtsAndThen ctxt tcMcStmt stmts ty_dummy $ \res_ty' ->
782 do { ids <- tcLookupLocalIds names
783 ; _ <- unifyType res_ty' (m_ty `mkAppTy` mkBigCoreVarTupTy ids)
784 ; (pairs', thing) <- loop m_ty pairs
785 ; return (ids, pairs', thing) }
786 ; return ( (stmts', ids) : pairs', thing ) }
789 = pprPanic "tcMcStmt: unexpected Stmt" (ppr stmt)
791 --------------------------------
793 -- The main excitement here is dealing with rebindable syntax
795 tcDoStmt :: TcStmtChecker
797 tcDoStmt _ (LastStmt body _) res_ty thing_inside
798 = do { body' <- tcMonoExprNC body res_ty
799 ; thing <- thing_inside (panic "tcDoStmt: thing_inside")
800 ; return (LastStmt body' noSyntaxExpr, thing) }
802 tcDoStmt ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
803 = do { -- Deal with rebindable syntax:
804 -- (>>=) :: rhs_ty -> (pat_ty -> new_res_ty) -> res_ty
805 -- This level of generality is needed for using do-notation
806 -- in full generality; see Trac #1537
808 -- I'd like to put this *after* the tcSyntaxOp
809 -- (see Note [Treat rebindable syntax first], but that breaks
810 -- the rigidity info for GADTs. When we move to the new story
811 -- for GADTs, we can move this after tcSyntaxOp
812 rhs_ty <- newFlexiTyVarTy liftedTypeKind
813 ; pat_ty <- newFlexiTyVarTy liftedTypeKind
814 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
815 ; bind_op' <- tcSyntaxOp DoOrigin bind_op
816 (mkFunTys [rhs_ty, mkFunTy pat_ty new_res_ty] res_ty)
818 -- If (but only if) the pattern can fail,
819 -- typecheck the 'fail' operator
820 ; fail_op' <- if isIrrefutableHsPat pat
821 then return noSyntaxExpr
822 else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy new_res_ty)
824 ; rhs' <- tcMonoExprNC rhs rhs_ty
825 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
826 thing_inside new_res_ty
828 ; return (BindStmt pat' rhs' bind_op' fail_op', thing) }
831 tcDoStmt _ (ExprStmt rhs then_op _ _) res_ty thing_inside
832 = do { -- Deal with rebindable syntax;
833 -- (>>) :: rhs_ty -> new_res_ty -> res_ty
834 -- See also Note [Treat rebindable syntax first]
835 rhs_ty <- newFlexiTyVarTy liftedTypeKind
836 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
837 ; then_op' <- tcSyntaxOp DoOrigin then_op
838 (mkFunTys [rhs_ty, new_res_ty] res_ty)
840 ; rhs' <- tcMonoExprNC rhs rhs_ty
841 ; thing <- thing_inside new_res_ty
842 ; return (ExprStmt rhs' then_op' noSyntaxExpr rhs_ty, thing) }
844 tcDoStmt ctxt (RecStmt { recS_stmts = stmts, recS_later_ids = later_names
845 , recS_rec_ids = rec_names, recS_ret_fn = ret_op
846 , recS_mfix_fn = mfix_op, recS_bind_fn = bind_op })
848 = do { let tup_names = rec_names ++ filterOut (`elem` rec_names) later_names
849 ; tup_elt_tys <- newFlexiTyVarTys (length tup_names) liftedTypeKind
850 ; let tup_ids = zipWith mkLocalId tup_names tup_elt_tys
851 tup_ty = mkBoxedTupleTy tup_elt_tys
853 ; tcExtendIdEnv tup_ids $ do
854 { stmts_ty <- newFlexiTyVarTy liftedTypeKind
855 ; (stmts', (ret_op', tup_rets))
856 <- tcStmtsAndThen ctxt tcDoStmt stmts stmts_ty $ \ inner_res_ty ->
857 do { tup_rets <- zipWithM tcCheckId tup_names tup_elt_tys
858 -- Unify the types of the "final" Ids (which may
859 -- be polymorphic) with those of "knot-tied" Ids
860 ; ret_op' <- tcSyntaxOp DoOrigin ret_op (mkFunTy tup_ty inner_res_ty)
861 ; return (ret_op', tup_rets) }
863 ; mfix_res_ty <- newFlexiTyVarTy liftedTypeKind
864 ; mfix_op' <- tcSyntaxOp DoOrigin mfix_op
865 (mkFunTy (mkFunTy tup_ty stmts_ty) mfix_res_ty)
867 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
868 ; bind_op' <- tcSyntaxOp DoOrigin bind_op
869 (mkFunTys [mfix_res_ty, mkFunTy tup_ty new_res_ty] res_ty)
871 ; thing <- thing_inside new_res_ty
872 -- ; lie_binds <- bindLocalMethods lie tup_ids
874 ; let rec_ids = takeList rec_names tup_ids
875 ; later_ids <- tcLookupLocalIds later_names
876 ; traceTc "tcdo" $ vcat [ppr rec_ids <+> ppr (map idType rec_ids),
877 ppr later_ids <+> ppr (map idType later_ids)]
878 ; return (RecStmt { recS_stmts = stmts', recS_later_ids = later_ids
879 , recS_rec_ids = rec_ids, recS_ret_fn = ret_op'
880 , recS_mfix_fn = mfix_op', recS_bind_fn = bind_op'
881 , recS_rec_rets = tup_rets, recS_ret_ty = stmts_ty }, thing)
885 = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt)
888 Note [Treat rebindable syntax first]
889 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
891 do { bar; ... } :: IO ()
892 we want to typecheck 'bar' in the knowledge that it should be an IO thing,
893 pushing info from the context into the RHS. To do this, we check the
894 rebindable syntax first, and push that information into (tcMonoExprNC rhs).
895 Otherwise the error shows up when cheking the rebindable syntax, and
896 the expected/inferred stuff is back to front (see Trac #3613).
899 --------------------------------
901 -- The distinctive features here are
903 -- (b) no rebindable syntax
905 tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference
907 -- Used only by TcArrows... should be gotten rid of
908 tcMDoStmt tc_rhs ctxt (BindStmt pat rhs _ _) res_ty thing_inside
909 = do { (rhs', pat_ty) <- tc_rhs rhs
910 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
912 ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
914 tcMDoStmt tc_rhs _ (ExprStmt rhs _ _ _) res_ty thing_inside
915 = do { (rhs', elt_ty) <- tc_rhs rhs
916 ; thing <- thing_inside res_ty
917 ; return (ExprStmt rhs' noSyntaxExpr noSyntaxExpr elt_ty, thing) }
919 tcMDoStmt tc_rhs ctxt (RecStmt { recS_stmts = stmts, recS_later_ids = laterNames
920 , recS_rec_ids = recNames }) res_ty thing_inside
921 = do { rec_tys <- newFlexiTyVarTys (length recNames) liftedTypeKind
922 ; let rec_ids = zipWith mkLocalId recNames rec_tys
923 ; tcExtendIdEnv rec_ids $ do
924 { (stmts', (later_ids, rec_rets))
925 <- tcStmtsAndThen ctxt (tcMDoStmt tc_rhs) stmts res_ty $ \ _res_ty' ->
926 -- ToDo: res_ty not really right
927 do { rec_rets <- zipWithM tcCheckId recNames rec_tys
928 ; later_ids <- tcLookupLocalIds laterNames
929 ; return (later_ids, rec_rets) }
931 ; thing <- tcExtendIdEnv later_ids (thing_inside res_ty)
932 -- NB: The rec_ids for the recursive things
933 -- already scope over this part. This binding may shadow
934 -- some of them with polymorphic things with the same Name
935 -- (see note [RecStmt] in HsExpr)
937 ; return (emptyRecStmt { recS_stmts = stmts', recS_later_ids = later_ids
938 , recS_rec_ids = rec_ids, recS_rec_rets = rec_rets
939 , recS_ret_ty = res_ty }, thing)
942 tcMDoStmt _ _ stmt _ _
943 = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt)
947 %************************************************************************
949 \subsection{Errors and contexts}
951 %************************************************************************
953 @sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same
954 number of args are used in each equation.
957 checkArgs :: Name -> MatchGroup Name -> TcM ()
958 checkArgs fun (MatchGroup (match1:matches) _)
959 | null bad_matches = return ()
961 = failWithTc (vcat [ptext (sLit "Equations for") <+> quotes (ppr fun) <+>
962 ptext (sLit "have different numbers of arguments"),
963 nest 2 (ppr (getLoc match1)),
964 nest 2 (ppr (getLoc (head bad_matches)))])
966 n_args1 = args_in_match match1
967 bad_matches = [m | m <- matches, args_in_match m /= n_args1]
969 args_in_match :: LMatch Name -> Int
970 args_in_match (L _ (Match pats _ _)) = length pats
971 checkArgs fun _ = pprPanic "TcPat.checkArgs" (ppr fun) -- Matches always non-empty